Paging systems have evolved into more robust communication systems capable of transmitting alphanumeric, voice and image data to portable receivers. Two-way paging systems are on the horizon. In a two-way paging system, the portable device transmits a limited content response signal which includes a reply message or an acknowledgment message in response to receiving a message. Thus, the term "messaging" is a broader term which encompasses the transmission of data messages, voice messages, facsimile messages, etc., as well as contemplating the transmission back from the portable or remote unit of a response signal which is a reply message or an acknowledgment message.
A messaging system comprising a plurality of message subscriber units (capable of receiving messages and transmitted response signals) will accommodate a variety of message types, some which require more "air-time", such as data messages and facsimile messages, than others. The challenge is to optimize the transmission of messages to message subscriber units so as to maintain a high system capacity. Part of this challenge involves transmitting messages only in those portions of a messaging system coverage area where the message subscriber unit is likely to be located.